“I was trained on 15s,”
While I was in the two-way radio business, RTTY was only a
ham radio adventure around 1965-1972. I had a few DX contacts from around the world, using my model 19.
I also remember a portable tty machine that I got through Army MARS, but do not remember the make or model.
I had no training on tty, much less any professional or business with them.
I also remember teletype art being popular. The most famous was the nude girl sitting on a stool. While I had a perf unit and tape reader, I never got into the art gig.
I gotta believe that the guys that created that became our first programmers. lol